Maria Bała

Shale Gas in Poland

An example of interpretation of the Silurian and Ordovician shale formations in the Baltic Basin in Poland regarding determination of potential sweet spots is presented. Short geological information shows the position of shale gas play. Description of the data—laboratory measurement outcomes (petrophysical and geochemical) and well logging—presents results available for analyses. Detailed elemental analyses and various statistical classifications show the differentiation between sweet spots and adjacent formations. Elastic property modelling based on the known theoretical models and results of comprehensive interpretation of well logs is a good tool to complete information, especially in old wells. Acoustic emission investigations show additional characteristic features of shale gas rock and reveal that acoustic emission and volumetric strain of a shale sample induced by the sorption processes are lower for shale than for coals.

The application of well logging and seismic modeling to assess the degree of gas saturation in Miocene strata (Carpathian Foredeep, Poland)

The presence of natural gas in the pore space of reservoir rocks results in a significant decrease in P-wave velocity. Even low gas saturation can generate seismic anomalies (DHI) and false image of gas accumulation of economic importance. This article presents an attempt to evaluate gas saturation from 2D seismic section in the Miocene sandstone strata in the south-eastern part of the Carpathian Foredeep. The ESTYMACJA program and the Biot-Gassmann model were used to study the dependence between elastic parameters and saturating fluids (water and gas) recorded in wells. Series of calculations was carried out using a method of fluid substitution for various gas saturation. The applicability of seismic data for evaluating gas saturation of reservoir beds was assessed with the use of 1D modelling (synthetic seismograms) and 2D modelling (theoretical seismic section) calculated for different gas saturation. The proposed methodology can be used to identify low and high gas-saturated zones and contour the reservoir.

New Methods for Modeling Laterolog Resistivity Corrections

The paper presents methods for laterolog response modeling. In Coulomb’s charges method, Laplace’s equation is solved for the electric field distribution in rock medium with internal boundaries between different resistivity layers. There, the boundary problem is reduced to Fred-holm integral equation of the second kind. The second method uses a finite element array to model apparent resistivity from laterolog. The task is treated as DC problem and the Laplace equation is solved numerically. The presented methods were applied to borehole data covering a typical stratigraphie section of the Fore-Sudetic Monocline in southwestern Poland. Apparent resistivity was calculated using the Coulomb’s charges method and alternatively modeled using a finite element method which gave similar results. Then, a series of linear corrections for borehole, shoulder bed, and filtration effects for apparent resistivity obtained by the Coulomb’s charges method demonstrated the feasibility of calculating true resistivity of virgin and invaded zones. The proposed methods provide a flexible solution in modeling which can be adapted to other logs.

Evaluating Electrical Anisotropy Parameters in Miocene Formations in the Cierpisz Deposit

ab]AbstractThe electrical anisotropy of rocks is generally an effect of alternating layers of thin-bedded sandstones and shales with clear lamination.Thin-bedded rock sequences can be treated as an anisotropic medium described by two resistivities: horizontally to the bedding RH and vertically to the bedding RV. Such sequences have fairly low resistivity and, as a result of poor vertical resolution of conventional electric tools, one can sometimes fail to distinguish them from the adjoining shales.This paper presents the possibility of calculating the anisotropy parameters based on resistivity logs recorded with a laterolog tool (DLL) and an induction tool HRAI. We have also performed an analysis of the ambiguity of the results and attempts to assess the water saturation (SW) generating cross-plots based on calculated resistivities, RH and RV.It is very important to correctly evaluate the resistivity of sandstone interbeds when calculating water saturation (SW) and hydrocarbon saturation (SG), in formulating an integrated quantitative interpretation of anisotropic formations.

Elastic Parameters of Rocks from Well Logging Even in Near Surface Sediments

Results of the computer program FalaFWS for processing and interpretation of acoustic full waveforms in deep and shallow rock formations are presented. The goal of the paper is to show a possibility of obtaining correct values of elastic properties of shallow formations on the basis of acoustic waveforms recorded with standard device. Results of measurements with a device constructed for deep wells and results of data interpretation using computer program written for that device provide an interpreter with correct values of dynamic elastic parameters in shallow, poorly consolidated rocks. Field examples are given to confirm the presented analysis.